Bacterial diversity associated with subalpine fir (Abies lasiocarpa) ectomycorrhizae following wildfire and salvage-logging in central British Columbia.

To assess the effect of fire and salvage logging on the diversity of mycorrhizal-bacterial communities, bacteria associated with Cenococcum, Thelephora, Tomentella, Russulaceae, and E-strain ectomycorrhizae (ECM) of Abies lasiocarpa seedlings were characterized using two approaches. First, bacteria were isolated and characterized by Biolog, gas chromatography fatty acid methyl ester (GC-FAME), and amplified 16S rDNA restriction analysis (ARDRA). The bacterial communities retrieved from ECM from both sites were dominated by Proteobacteria (groups gamma and beta). Pseudomonas was the most common genus isolated, followed by Variovorax, Burkholderia, and Xanthomonas. Gram-positive isolates (mostly high-G+C Gram-positive bacteria) were more frequently retrieved on the burned-salvaged site, many commonly associated with the two ascomycete ECM, Cenococcum and E-strain. Pseudomonas species were retrieved more frequently from Thelephora. Although actinomycetes were isolated from all sites, almost no actinomycetes or other Gram-positive bacteria were isolated from either Thelephora or Tomentella. Second, amplified 16S rRNA gene sequences were amplified directly from root tips and then cloned into the plasmid vector pAMP1, followed by restriction analysis. This technique distinguished more genotypes than isolates retrieved by culturing methods, but generally, results were similar in that the largest proportion of the bacteria were putatively Gram-negative; putative Gram-positive bacteria were fewer and most were from the burned-salvaged site. Direct cloning resulted in many patterns that did not match any identified isolates, suggesting that a large proportion of clones were unique or not culturable by the methods used. Analysis for both protocols showed no significant difference in bacterial diversity between the burned-salvaged and unburned sites.

Effects of sulphur dioxide fumigation on Phleum pratense and vesicular-arbuscular mycorrhizal fungi.

Two experiments were conducted using controlled environment SO2 fumigation chambers which allowed only the shoots of Phleum pratense to be fumigated. Experiment 1 examined the effect of SO2 fumigation on the ability of vesicular-arbuscular (VA) mycorrhizal fungi to infect roots. Experiment 2 examined the effect of SO2 fumigation on the proliferation of VA mycorrhizas in the roots. There was a significant decrease in the amount of infection in the roots of plants exposed to SO2 . Low concentrations (0.05-0.07 µ 1-1 ) of SO2 affected the ability of VA mycorrhizal fungi to colonize and, also, to proliferate within roots. In both experiments, root colonization was the overriding factor affecting the number of tillers, leaf area, and shoot and root dry weights of infected plants. Increased VA mycorrhizal infection resulted in reductions in the plant growth parameters.